1. Field of the Invention
This invention relates to an upper control arm for a vehicle suspension system and, in particular, to a lightweight yet strong control arm and a method of making such control arms.
2. Description of the Prior Art
Upper control arms are routinely incorporated into the suspension systems of truck and passenger vehicles. The typical control arm is generally U-shaped with a ball joint assembly at the apex of the control arm and pivot bar bushings at the ends of the arm for mounting the control arm to a pivot bar assembly. In the past, the modulus sections between the bushings and the ball joint have been solid sections of cast iron or cast aluminum. It was believed that the traditional cast metal sections were necessary to maintain the integrity of the control arm under the stresses of the suspension system. More recently, the modulus section has been constructed of a steel forging of wire frame design. Although these control arm constructions were strong enough to withstand the stress loads they also were very heavy. In today's vehicle market every aspect of a vehicle is examined for weight reduction.
Recent proposals for reducing the weight of the suspension system include a hollow, two-piece control arm. The square hollow bar section comprises a pair of U-shaped components nested together and double seam welded. Thus, the control arm has double side walls with single upper and lower walls. Although strong and lightweight, the double side walls are not located at the compressive stress areas of the arm where additional strength is required. Moreover, the double seam construction requires precise welding over a curving contour which has not been easy to accommodate. Nevertheless, substantial weight reduction over the solid cross-section of the prior known control arms has been accomplished.